Microorganisms are usually cultivated in apparatuses provided with agitation means or stirrers to ensure that the fermentable liquid is uniformly mixed throughout the entire inner volume of the apparatus. When growing microorganisms tending to produce filamentous mycelium, no prior art apparatus can assure uniform distribution of the living cells because the walls and the stirrer thereof become grown with clots of mycelium. Some mycelium clots float freely in the fermentation liquid and therefore are subject to mechanical destruction during stirring.
The supply of nutrient media to the mycelium being cultivated in the heretofore described conditions and the withdrawal of a metabolic product from the apparatus become too complicated, while some mycelium in the newly formed clots tend to die. This in turn results in that the growth of mycelium microorganisms tends to become uncontrollable, therefore rendering practically impossible the continuous cultivation of the mycelium forms of microorganisms. Accordingly, the principle whereby microorganisms are distributed uniformly throughout the fermentation liquid cannot be adopted in the case of cultivating mycelium microorganisms.
Known in the art is an apparatus for cultivating tissue cells of a horizontal type comprising a housing partially filled with liquid nutrient media, the housing also accommodating a shaft of an agitation means provided with disk elements serving as carrying surfaces for the tissue cells (cf. USSR Inventor's Certificate No. 579,302 Cl. C 12 b 1/10).
The above apparatus is not provided with means for controlling the thickness of the layer of living cells growing on the surfaces of the disk elements, the cells thereby tending to fill the gaps between the disk elements. The apparatus needs to be disassembled in order to evacuate the cells from the gaps.
Mass transfer of the cells with the fermentation liquid is effected by immersing the disks into the substrate, which makes it impossible to carry out a continuous flow-through of the substrate to feed the cells.
Also known is a fermentation apparatus comprising a housing filled with fermentable liquid and accommodating a shaft of an agitation with stirrers (cf., e.g., U.S. Pat. No. 3,801,468, Cl. 195-141, published 1974).
The above apparatus is further provided with ribs or baffles secured to the inner wall of the apparatus and serving to guide the flow of the fermentable liquid.
Cultivation of microorganisms in the apparatus is accompanied by the formation of growths of living cells on the interior surfaces. However, the thickness of the layer of cells is non-uniform and cannot be effectively controlled. Further, the layer cannot be effectively fed with the nutrient media, while some of the cells inside the layer are liable to die, thus rendering a continuous controllable cultivation impossible.